Drill pipe shock absorber



March 28, 1961 D. E. MARQUIS ET AL 2,976,930

DRILL PIPE SHOCK ABSORBER Filed Aug. 1, 1958 ACCUMULATOR INVENTORS D.E.MARQUIS G.F. H W

u if? MILLER BY .PATTERSON MM W 6- 5O TON JACKS FIG. 2

A TTORNE KS DRILL PIPE SHOCK ABSORBER Duane E. Marquis, Bartlesville,Okla., Glenn F. Miller, Odessa, Tern, and Hugh W. Patterson,Bartlesville, Okla, assignors to Phillips Petroleum Company, acorporation of Delaware Filed Aug. 1, 1958, Ser. No. 752,523

8 Claims. (Cl. 166-85) This invention relates to-well drilling. -In oneaspect this invention relates to an apparatus for absorbing orcushioning shock incident to handling drill pipe within a bore hole.

In the drilling of a bore hole or well such as a gas or oil well, it isfrequently necessary to lower into and withdraw from the hole rods ortubing, generally referred to hereinafter as drill pipe, which supportbits or other drilling devices. The withdrawing and replacement of suchdrill pipe are necessary, for example, to change bits or other purposes.It is known in the art to use elevators, slips and the like to supportthe string of the drill pipe during such operations. The drill pipe,when in use, is frequently rotated by means of a kelly and a rotarytable. When the string is lowered onto the table, the table is subjectto impacts of enormous amounts when the string is brought to rest, sincethese strings are fre quently several thousands of feet long and ofgreat weight. These impacts may be so great as to fracture the drillpipe or to damage the rotary table. In wells of 10,000- l5,000 feet orless, the tubes are generally prepared of relatively soft steel andslips are generally employed for supporting the weight of such stringssince slips are readily placed and removed from the tubes. Althoughslips tend to bite into the surface of the steel drill pipe, this is notunduly harmful with the soft steel. In deep wells, e.g. over 10,000 to15,000 feet in depth, the first 10,000 to 15,000 feet is frequently ofsoft steel and over this depth high tensile steel drill pipe is added tothe string. However, since slips tend to notch the pipe they are notdesirable for use on the harder high tensile steel pipe which has muchgreater notch sensitivity. Such pipes when notched, have a tendency tofail as the result of such notches. Therefore, with such drill pipe,elevators are preferred for handling same. Since elevators have nocushioning effect when the weight of the drill string is placed on therotary table it is desirable to provide some cushioning means. Whenremoving strings from bore hole, the string is raised a section length,a slip or elevator placed around the string, the string supported on therotary table and the top section removed from the string. This processis continued until all of the string is removed. In lowering the string,the process is reversed, a section at a time being added.

:It is an object of this invention to provide means for minimizingdamage due to handling tool strings when placing or measuring same froma drill hole.

Other objects, features and advantages of this invention will be obviousto one skilled in the art having been given this disclosure.

The apparatus of this invention comprises a plate adapted to slip undera string lifting means and supported on a plurality of hydraulic jack-sconnected through metering means to a common gas cushioned liquidaccumulator.

The apparatus of this invention is broadly operable for handling borestrings generally and is particularly de- States Patent sir-able for usein conjunction with an elveator on strings of 15,000 feet in length orover.

This invention will be further described in conjunction with theattached figures of which: 1

Figure l is an elevation of a preferred embodiment of the apparatus ofthis invention; and

Figure 2 is a schematic showing of the piping arrangement of thisinvention.

Referring now to the drawings, plate 1 has a cylindrical riser 2 to fitaround a well string and having slot 3 therein so that the entireapparatus can be slipped around the string. A plurality of guidecylinders 4 (four in the drawing) are provided for holding the top plate17 in place. Also supported on plate 1 are a plurality of hydraulicjacks 5 (six in this embodiment) spaced on support plate 1 to'distributethe load applied to the top plate equally. These jacks 5 are operablyconnected to accumulator 12 via conduits 6, 7 needle valve 8 and conduit9. Needle valve 8 is by-passed with conduit 10 and check valve 11 whichpermits free flow of fluids from accumulator 12 toward jacks 5, butprevents flow in the opposite direction. Pressure'release valve 13 isprovided between the jacks 5 and the check valve 11 and needle valve 8as a safety means should the shock applied to the jacks become too greatfor the hydraulic system. As shown, this check valve releases into thecenter of the riser 2. Pressure gage 14 is operably installed throughneedle valve 15 in the conduit between the jacks and valves 8 and 11.Rods 16 are provided for securing the cover plate to the shock absorbingas sembly.

Cover plate 17 is provided with a plurality of studs 18 matched to thecylinders 4 on the base plate 1. This plate is provided with a cut-away19 to fit around the string. It is within the scope of this invention toprovide a shield or metal plate extending downward from the circularportion of slot 19 to fit inside the correspond-I ing portion of riser2. This shield prevents mud and the like from running from the drillpipe into the apparatus. A cover plate can be provided for the rest ofkeyway 19 and this cover platecan also be provided with metal shieldsextending downward toward the base plate. It is alsowithin the scope ofthis invention to provide a skirt around the outer circumference of theassemblypreferably attached to and depending from the top plate.

Cover plate 17 is also provided with drilled and tapped holes 20 intowhich pins 16 are threaded. Pins 16 extend downwardly through drilledholes in lugs or brackets 21 and have locking nuts 22 on their lowerends. Thus, upper plate 17 is permitted to move downwardly but isprevented from moving upwardly a distance greater than that permitted bythe free length of pins 16. Pins 16 also prevent the top plate 17 frombeing removed from the assembly as might occur if the entire assemblywere picked up by the top 'plate. In general, the locking nuts 22 willbe tightened at least sufiiciently to hold the cover plate 17 firmlyagainst the jacks 5 and preferably sufiicient to depress the jacks ashort distance, less than an inch, e.g., one-half inch.

The accumulator 12 can be of any conventional design and is soconstructed that liquid flows through conduit 9 from the jacks into theaccumulator and the liquid is cushioned by compressing a gas. In theparticular embodiment, the liquid and gas phase is separated by apiston; however, a diaphragm or other separating means can be used,e.g., liquid gas interface.

The cut-away 19 in cover plate 17 can be the same or different from thatof the base plate. For example, the same base assembly can be used on avariety of strings of different diameters by providing a plurality ofcover plates keyed to fit difierent size strings. I While the drawingshows six jacks 5, four pins 16 and 3 four cylinders 4 on the baseplate, these can vary as desired depending upon the total load and jackcapacity, etc. It is desirable to have at least three jacks so that theload can be stabilized on the base plate 1 and at least two aligningcylinders 4 and studs 18 to keep the top plate aligned with the shockassembly. The pins 16 are optional, but are desirable in order to keepthe top plate fastened tight against the supporting jacks. The safetyvalve 13 and gage 14 are optional equipment that will generally beemployed for reasons of safety and convenience. Check valve 11 is anoptional piece of equipment which permits better operation of theaccumulator and jacks when the load is suddenly removed. Needle valves15 and 8 can be replaced by any suitable means such as an orifice orsmall pipe to regulate the flow of liquid from the jacks in theaccumulator and prevents the effect of a hydraulic hammer on theaccumulator when load is suddenly applied. The needle valves areadvantageously employed since they provide a ready and easily adjustablemetering means.

In using the apparatus of this invention the drilling string is raisedand lowered by conventional hoisting equipment common to all present daydrilling rigs of the rotary type. Since it has been found that the slipscustomarily used to engage the pipe for supporting it from the rotarytable are undesirable, a sequence of operation using two sets ofelevators will be described. Assuming that drilling has been inprogress, the drill string is raised by means of the hoisting equipment(draw works) and the shock absorber placed in position around the drillpipe. An elevator can then be placed around the drill pipe and theentire drill string lowered till the first threaded connection (tooljoint) rests on the elevator. The Kelly joint is then broken off andplaced to one side. The elevator is then attached to the travelingblocks by means of balls and the entire string hoisted to the desiredheight-usually 3 lengths of drill pipe or about 90 feet. At this pointanother threaded connector (tool joint) will have been raised above theshock absorber and a second elevator is installed between the top plateof the shock absorber and the tool joint. As the string is lowered, theweight of the drill pipe will come to rest on the elevator and this inturn will transfer the weight to the shock absorber. As the additionalweight is imposed on the shock absorber the top plate will movedownwardly and there will be increasing resistance to movement. Thus theshock absorber will bring the pipe to a cushioned stop and preventsudden shock loads. The

lengths of drill pipe just above the tool joint resting on the shockabsorber can now be unscrewed and set off to one side in the derrick.The first elevator is disengaged from the upper end of this length ofpipe and is lowered to the derrick floor. The elevator bails are thentransferred to the second elevator which now is suspending the drillpipe and the process repeated until all drill pipe is out of the hole.Drill pipe can be run back in the well by using the reverse of the abovedescribed process.

The advantages of this device are many. First, the shock absorber ofthis invention offers increasing resistance with increasing displacementthereby providing a smooth cushioning efiect. The absorber of thisinvention is readily installed on the drill string by means of thekeyways or cut-away.

A shock absorber constructed as shown in Figure 1 utilizing 2 inch platefor the base and cover plates, six ton jacks, and a Parker HydraulicAccumulator was used for lowering pipe into a well in excess of 15,000feet. The four pins used for securing the top plate of the lowerassembly were 1 inch in diameter and the guide studs and cylinder wereof 5 inch diameter. In lowering 270,000 pounds of string, the devicecushioned the drill string to a stop during 4 inches of travel bymetering the fluid flow from the six pistons arranged in a circlethrough needle valves to the nitrogen charged piston type accumulator.

can be made and still obtain the advantages of this invention.

While we have described our invention for use in handling drill pipe ina well being drilled, it is of course obvious that the apparatus can beused with equal results in handling any other long string of steel goodssuch as well casing, well tubing or slicker rods.

While the preferred embodiment of the invention is described through theuse of two sets of elevators, it is entirely feasible to use the shockabsorber in the conventional manner with one set of elevators and a setof slips. It will be readily understood by one skilled in the art thatthe shock absorber could have a slip receiving bowl attached to the topplate of the assembly. This bowl could be removably installed above thetop sur-- face of the top plate of the shock absorber or could berecessed in the top plate. While the use of slips would not entirelyeliminate the possibility of damage to the drill pipe, the shockabsorber would still provide protection against sudden shock loads andthus would afford an overall system superior to that in common industryuse.

We claim:

1. An apparatus for absorbing shocks from a well string being movedwithin a bore hole comprising, in combination, a base plate providedwith a central opening for said string, a cover plate provided with acentral opening for said string, and hydraulic shock absorbing meansbetween said plates comprising cylinder and piston assemblies, saidassemblies being operably connected to hydraulic accumulator means toreceive hydraulic fiuid from said assemblies when a load is applied tosaid cover plate.

2. Apparatus according to claim 1 wherein aligned slots extend from thecentral opening to the edge of each of said plates so that saidapparatus can be centered on said string from the side thereof.

3. An apparatus for absorbing shock from a well string being movedvertically within a bore hole comprising, in. combination, a base plateprovided with a central opening for said string, a plurality ofhydraulic cylinder and piston assemblies mounted on said base plate inspaced relationship, a common hydraulic accumulator operably connectedto said assemblies through a valved conduit, a cover plate provided witha central opening for said string resting on said assemblies, said coverplate being adapted to support said string, guide means connecte to saidcover plate to align said cover plate on said assemblies, and a slot ineach said plate extending from the central opening to the edge of theplate, said slots being aligned so that said apparatus can be centeredon said string from the side thereof.

4. Apparatus according to claim 3 wherein there are at least threehydraulic cylinder and piston assemblies.

5. Apparatus according to claim 4 wherein the valve in said valvedconduit is a needle valve.

6. An assembled apparatus for absorbing shock from a well string beingmoved vertically within a bore hole comprising, in combination, a baseplate provided with a central opening for said string, at least threehydraulic cylinder and piston assemblies anranged in spaced relationship in a ring on said base plate and secured thereto, a hydraulicaccumulator mounted on said base plate operably connected to saidassemblies by a first valved conduit, said accumulator being alsoadapted to accumulate hydraulic fiuid against a gas cushion, a secondvalved conduit connecting said assemblies with said ac cumulator adaptedto permit fluid flow from said accumulator to said assemblies, a coverplate provided with a central opening for said string resting on saidassemblies. said cover plate being adapted to receive the weight of saidwell string, sleeved guide means connected to said plates to align saidcover on said assemblies, securing means connected to said plates toprevent said cover from moving away from said base plate beyond a preThose skilled in the art will see many changes which deter-mineddistance upon removal of a load from said cover plate, and a slot ineach said plate extending from said opening to the edge of the plate,said slots being aligned so that said assembled apparatus can becentered on said string from the side thereof.

7. Apparatus according to claim 6 wherein the valve 5 1503131 NelsonJuly 1,517,979 Greathouse Dec. 2, in said first conduit 1s a needlevalve and the valve 111 1966 454 M d J l 17 1934 said second conduit isa check valve. 0057 Y y 8. Apparatus-according to claim 7 wherein apressure 7 err relief valve is provided between said needle valve and2,300,162 Maude said assemblies, said pressure relief valve being set ata 10 2,756,989 PeTas July predetermined maximum pressure.

References Cited in the file of this patent UNITED STATES PATENTS

